Revising A Failed First MPJ Implant In A Patient With Chronic Pain

These authors offer pertinent insights on treating a 45-year-old woman who complained of severe pain years after receiving a total first metatarsophalangeal joint (MPJ) implant.

A patient presented with a chief complaint of severe pain in her left foot and noted that she had a total first metatarsophalangeal joint (MPJ) implant procedure in 2008, two years prior to presentation. She was 45 years old and had normal height to weight proportion.

   The patient related that after her first surgery for a painful first MPJ, she had some improvement one day and pain the next day. However, after several months, she developed constant, significant pain. At the time of her presentation in January 2010, she was still wearing a surgical shoe because she was unable to wear a regular shoe. Her gait was significantly altered. She did not have any current psychological manifestations.

   She had already seen five other specialists including orthopedic surgeons, who all recommended fusion of the first MPJ. Multiple pain management specialists had treated the patient for chronic pain. She had received a diagnosis of complex regional pain syndrome (CRPS). She was reluctant to undergo fusion surgery, remained unsatisfied and presented for diagnosis and treatment.

What The Examination Revealed

The patient had a very positive Tinel’s sign and provocation sign of the common peroneal nerve in the left leg. She had no tenderness on her common peroneal nerve at the level of the fibular neck on her right side. The Tinel's sign caused a distal radiation into her entire foot. She also demonstrated a significant Tinel’s sign of the left medial ankle over the tibial nerve.

   The patient could not tolerate even the lightest touch in the first MPJ area. She had a well-healed surgical scar on the dorsal aspect of her first MPJ, which she was unable to tolerate even the lightest touch. She had hypersensitivity on the plantar aspect of her left foot.

   Her motor strength was greatly decreased to the point where she could not even raise her hallux, demonstrating no extensor hallucis longus function. She also had no eversion or inversion motor strength. She had full motor strength 5/5 on the right side of all muscle groups.

   A review of radiographs demonstrated that she had significant hypertrophic bony development and involution of a short-stemmed Swanson Silastic implant (Wright Medical Technology) without grommets. She was unable to tolerate any examination regarding range of motion of the first MPJ because of allodynia. There was no limitation of dorsiflexion at the ankle joint with her knee extended. Her skin texture was normal and there was abnormal temperature.

   Based on the exam, we diagnosed her with the following conditions in her left lower extremity: CRPS, entrapment of the common peroneal nerve, tarsal tunnel syndrome and a failed first MPJ implant.

A Guide To First MPJ Treatment And Pain Relief

We explained to the patient that her first MPJ had developed as a primary pain generator due to detritic synovitis and chronic inflammation. She subsequently developed entrapment of her tarsal tunnel and common peroneal nerve. This entrapment contributed to her chronic pain syndrome due to compensation from the pain at the level of the first MPJ. In addition to her change in gait, postoperative swelling and the long periods of immobilization contributed to her multiple nerve entrapments. She was unable to undergo Pressure Specified Sensory Device (PSSD, Sensory Management) neurosensory testing because she would not be able to tolerate the testing due to the hypersensitivity in her left foot.

   We performed the following procedures:
1. Neurolysis/decompression of left common peroneal nerve
2. Neurolysis/decompression of the tibial nerve, medial plantar nerve, lateral plantar nerve and medial calcaneal nerve with endoscopic tarsal tunnel decompression
3. Revision arthroplasty with replacement of the Swanson short-stemmed implant with grommets.

   The patient understood that due to her CRPS, she would be required to have an epidural block in addition to the general anesthetic. She started on gabapentin (Neurontin, Pfizer) preoperatively. We also advised her that because of the severity of her pain syndrome, it was unrealistic to expect a complete reduction of pain. However, we noted that she should expect significant improvement and be able to wear a normal shoe without pain. She understood that additional denervation surgery could be required. There was an extensive discussion with her about her current mental status — specifically whether she was depressed — in order to gain some insight into whether she needed psychiatric treatment prior to surgery.

   Based on direct questioning of the patient as well as her ability to demonstrate in our discussion that she had realistic expectations, did not admit to any depression or anxiety, and understood the likelihood of not attaining a 100 percent result, we determined that there were no psychological issues and that the patient had a strong understanding of the benefits and risk of the surgery. (We routinely use the PHQ-9 depression questionnaire to rule out clinical depression.) We were also able to determine that her pain was not centrally mediated as she had no pain if there was no weight bearing or movement in her left foot.

   We encountered significant scar tissue around the left first MPJ but the bone quality was good. Using loupe magnification in this area, we isolated and performed neurolysis of several small nerve branches. The common peroneal nerve was severely entrapped as evidenced by an “hourglass” deformity.

Why Clinicians Should Be Wary About Assumptions About The Source Or Sources Of Pain

This case illustrates a very complex foot syndrome, which five specialists, including orthopedists and podiatrists, previously under-diagnosed. Interestingly, the patient related that all five previous physicians recommended fusion of the first MPJ. However, none of the physicians had even examined her proximally to determine that she also had serious peripheral nerve entrapment, which was an overall major contributor to her pain syndrome. The universal assumption was that her pain was coming from her joint pain, nothing more.

   This illustrates how we can become very biased and have “tunnel vision” when patients present to us with a “defined” problem.

   Fusing the first MPJ in a fit 45-year-old patient can lead to significant biomechanical impairment. The patient was adamant against first MPJ fusion. The subsequent pathomechanics resulting from a first MPJ fusion would ultimately lead to a breakdown of the lateral forefoot and have additional translation to the lower extremity of aberrant mechanics with subsequent pathology.

   The patient is now more than two years post-op and is completely free of pain with normal gait and full pain-free function. She takes no pain medications or anticonvulsants.

What We Can Learn From This Case

• When a patient presents with a previously failed surgery, especially in the forefoot, it is vitally important to evaluate the entire patient to see if there is coexistent proximal pathology, such as equinus or peripheral nerve entrapment.

• Determine the psychology of the patient in order to frame a goal of his or her expectations of a positive outcome.

• It is perfectly acceptable to operate on a patient with chronic pain as long as one takes the perioperative measures consisting of pre-op medication (NSAIDs and anticonvulsants), a spinal or epidural block, administration of ketamine during the case, pre-emptive local anesthetic analgesia and meticulous postoperative pain management.

• Do not place a short-stemmed Swanson implant without grommets.

   Dr. Barrett is an Adjunct Professor within the Arizona Podiatric Medicine Program at the Midwestern University College of Health Sciences. He is a Fellow of the American College of Foot and Ankle Surgeons.

   Dr. Lee is in private practice in Dallas, Texas.